| 摘要 |
<p>Steel pipe 20 is coated by coextruding a composite heat softenable sheet 18, comprising a lower layer 14 of thermoplastic adhesive and an upper layer 18 of protective thermoplastic onto the surface of the pipe 20 as it is simultaneously rotated and advanced axially to form thereon a helical wrap having an overlapping or a butt seam. A heat-shrinkable tape 22 may be applied over the helical seam. The composite sheet 18 can be applied to the steel surface with or without first priming and/or heating the pipe 20. <IMAGE></p> |
